In the field of couplings for pressurized fluid pipes, a safety problem may appear when the residual pressure in a fluid pipe connected to a coupling element reaches a high value, for example when the temperature of a fluid contained in this pipe increases, which causes an increase in the pressure of this pipe. In case of high pressure in the inner volume of a coupling element, it may be difficult to couple the two elements of a coupling member to connect two conduits. In some cases, such an overpressure may damage certain components of a circuit connected to a conduit experiencing an overpressure.
To resolve this problem, it is known, for example from U.S. Pat. No. 4,703,774 or CN-A-104,567,521, to install, within a closing valve of a coupling element, a bead subject on the one hand to the pressure prevailing within this coupling element, and on the other hand to the action of a return spring and the ambient pressure. This bead forms a relief valve for the coupling element in case of overpressure. It makes it possible to limit the pressure of the fluid within the coupling element. This solution is suitable for an underwater coupling, like that considered in U.S. Pat. No. 4,703,774, which may have relatively large dimensions. Conversely, it is difficult to implement with a coupling having smaller dimensions, since the available space at the center of the coupling element may be insufficient to house a bead with an appropriate size. Furthermore, the operating range of the relief valve formed by the bead is relatively limited. A high pressure is necessary within the coupling element to separate the bead from its seat, i.e., the trigger the discharge of the fluid, against the action exerted by the return spring.
Furthermore, the coupling elements known from DE-A-41 14 480 or U.S. Pat. No. 4,989,630, which have no relief member, do not make it possible to react to a pressure increase in the inner channel of these coupling elements.